Leap Year/Calendar Program. toString() method error.

I am implementing a class called GregorianCalendar. However, I am stuck on the method toString(). When I run my code has i get the output:
1, March 19, 2012 occurred in a leap year. I need the '1' to convert to the day, 'Monday'.

Code Java:

---

package gregoriandatetesterapp;
 
/**
 *
 * @author Jarrod
 */
public class GregorianDate 
{
    /**
     * integer representing the day
     */
    private int day;
 
    /**
     * integer 1-12 representing the month
     */
    private int month;
 
    /**
     * integer representing the year
     */
    private int year;
 
    /**
     * creates a date object that represents January 1, 1970
     */
    public GregorianDate()
    {
        month = 1;
        day = 1;
        year = 1970;
    }
 
    /**
     * creates a date object.
     * @param mm - the month of the specified date
     * @param dd - the day of the specified date
     * @param yy - the year of the specified date
     * @throw java.lang.IllegalArgumentException - when date is not valid
     */
    public GregorianDate(int mm, int dd, int yy)
    {
        if (mm < 1 || mm > 12)
            throw new IllegalArgumentException("This is not a valid month");
        if (dd < 1 || dd > 31)
            throw new IllegalArgumentException("This is not a valid day");
        if ((mm == 4 || mm == 6 || mm == 10 || mm == 11) && dd == 31)
            throw new IllegalArgumentException("This is not a valid date");
        if (mm == 2 && isLeap() && dd > 28)
            throw new IllegalArgumentException("This is not a valid date");
        if (mm == 2 && dd > 28)
            throw new IllegalArgumentException("This is not a valid date");
 
        month = mm;
        day = dd;
        year = yy;
    }
 
    /**
     * gives a number representing the day of the week of this date
     * @return a number 0-6 representing the day of the week on which this date occurs. 0 = Sunday, 1 = Monday, etc
     */
    public int dayOfWeek()
    {
       int u = 2*(3-((year/100)%4));
       int v = year%100;
       int w = v/4;
       int x = 0;
 
       if (isLeap() == false)
       {
            if (month == 1)
                x = 0;
            if (month == 2)
                x = 2;
            if (month == 3 || month == 11)
                x = 3;
            if (month == 4 || month == 7)
                x = 6;
            if (month == 5)
                x = 1;
            if (month == 6)
                x = 4;
            if (month == 8)
                x = 2;
            if (month == 9 || month == 12)
                x = 5;
            if (month == 10)
                x = 0;
       }
       else
       {
           if (month == 1)
               x = 6;
           if (month == 2)
               x = 2;
           if (month == 3 || month == 11)
                x = 3;
           if (month == 4 || month == 7)
                x = 6;
           if (month == 5)
                x = 1;
           if (month == 6)
                x = 4;
           if (month == 8)
                x = 2;
           if (month == 9 || month == 12)
                x = 5;
           if (month == 10)
                x = 0;
       }
 
       int y = u + v + w + x + day;
 
       return y%7;
    }
 
    /**
     * determine whether a year is a leap year.
     */
    public boolean isLeap() 
    {
       if (year%400 == 0 || (year%100 != 0 && year%4 == 0))
           return true;
       else 
           return false;
    }
 
    /**
     * gives the month in words
     * @param monthNum - a number 1-12 representing a month
     * @return the month in words with only its first letter in uppercase.
     */
    public java.lang.String monthToString(int monthNum)
    {
        month = monthNum;
 
        if (monthNum == 1) 
            return "January";
        if (monthNum == 2)
            return "February";
        if (monthNum == 3)
            return "March";
        if (monthNum == 4)
            return "April";
        if (monthNum == 5)
            return "May";
        if (monthNum == 6)
            return "June";
        if (monthNum == 7)
            return "July";
        if (monthNum == 8)
            return "August";
        if (monthNum == 9)
            return "September";
        if (monthNum == 10)
            return "October";
        if (monthNum == 11)
            return "November";
        if (monthNum == 12)
            return "December"; 
        else 
            return "Invalid Month";
    }
 
    /**
     * gives the day of the week in words
     */
    public java.lang.String weekdayToString(int dayNum) 
    {
        day = dayNum;
 
        if (dayNum == 0)
            return "Sunday";
        if (dayNum == 1)
            return "Monday";
        if (dayNum == 2)
            return "Tuesday";
        if (dayNum == 3)
            return "Wednesday";
        if (dayNum == 4)
            return "Thursday";
        if (dayNum == 5)
            return "Friday";
        if (dayNum == 6)
            return "Saturday";
        else
            return "Invalid Day";
    }     
    /**
     * gives a string representation of this object
     */
    public java.lang.String toString() 
    {
       String ds  = new Integer(dayOfWeek()).toString();
       ds = ds + ", ";
       ds = ds + monthToString(month);
       ds = ds + day;
       ds = ds + ", ";
       ds = ds + year;
       return ds;  
    }
}

---

Code Java:

---

package gregoriandatetesterapp;
 
import java.util.*;
import java.lang.*;
 
public class GregorianDateTester 
{
    public static void main(String[] args) 
    {
        int month, day, year;
 
        Scanner keyb = new Scanner(System.in);
        System.out.print("Enter numeric values for the month, day and year> ");
        month = keyb.nextInt();
        day = keyb.nextInt();
        year = keyb.nextInt();
 
        GregorianDate gd = new GregorianDate(month, day, year);
 
        if (gd.isLeap())
            System.out.println(gd + " occurred in a leap year.");
        else
            System.out.println(gd + " occurred in a non-leap year.");
 
    }
}

---

So output is currently looking like this:
Enter numeric values for month, day and year of a date> 3 20 2012
2, March 20, 2012 occurred in a leap year.

I need output to look like this:
Enter numeric values for month, day and year of a date> 3 20 2012
Tuesday, March 20, 2012 occurred in a leap year.

Change the toString method to return the day of the week instead of an Integer value.

Can you show the correction?

The code in the toString() method should be changed to return the values you want to see.
The thing you want to change is the first part of the String that is now an Integer.
Where is the value you want first in the String instead of a number?